الفهرس 
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Abstract
Habdomyosarcoma (RMS) is the most common form of soft-tissue sarcoma, accounting for 4.5% of all cases of childhood cancer. It is the third most common extracranial solid tumor of childhood after neuroblastoma and Wilm’s tumor. RMS is a malignant tumor of mesenchymal origin. It is included in the group of small blue round cell tumors of childhood along with neuroblastoma, lymphoma (Huh et al., 2010). The most prominent sites involve head and neck structures (~40%), genito-urinary track (~25%), and extremities (~20%). Embryonal (ERMS) and alveolar (ARMS) are the two major RMS subtypes that are distinct in their morphology and genetic make-up. The prognosis for this cancer depends strongly on tumor size, location, staging, and child’s age. In general, ERMS has a more favorable outcome, whereas the mortality rate remains high in patients with ARMS, because of its aggressive and metastatic nature (Abraham et al., 2011). In an effort to tailor the intensity of therapy to patient outcomes, the STS Committee of the Children’s Oncology Group has developed a risk-stratification system that incorporate pretreatment staging (based on anatomic site and TNM status) and extent of disease after surgical resection (clinical group). This stratification system is continually changing as new information becomes available but its current format (Leaphart et al., 2007)